I'm pretty sure my question is not well put so I will try to explain it little bit more. Let's say I have a Attiny85 without any firmware. What kind of firmware do I need to flash Attiny with, in order for Windows OS to recognize it as serial device connected via USB and assign it COM port for communication?
I don't want to install any additional drivers in OS, I would like Windows to use already preinstalled CH341S64 winchiphead drivers for USB to serial conversion.
Also I won't use any kind of bootloader on the Attiny itself for prototyping.